1. Field of the Invention
The invention relates to an apparatus for reproducing information from an optically readable record carrier on which digital information is stored in the form of a track of optically detectable areas which alternate with intermediate areas, which apparatus comprises:
an optical system for projecting a light beam on the record carrier,
at least two optical detectors which are so arranged in the beam which has been modulated by the record carrier that in the case of a correct tracking the two detectors are disposed symmetrically with respect to the image of the track,
a signal-generating circuit for generating at least a first and a second detection signal as a function of the amounts of light detected by the optical detectors, and
a control-signal generator for generating at least one signal which is a measure of the location of the spot produced by the light beam relative to the track.
2. Description of the Related Art
Such apparatus is known inter alia as the commercially available "Compact Disc Digital Audio" player which is described in "Philips Technical Review", Vol. 40, 1982, No. 6, the entire issue, which entire issue is herewith incorporated by reference, such a player being also described in, for example Japanese Patent Application No. 56-49094.
In the known apparatuses various control signals are derived in an analog manner from the digital signals originating from the disc, which control signals often exhibit a very low signal-to-noise ratio and often are also inaccurate because the control information is disturbed by the irregular data signal.